nacreous clouds

another awesome sky show i showed up too late to see.

Nacreous clouds glow brightly with vivid iridescent colours. They are wave clouds and their undulating sheet-like forms reveal the winds and waves of the stratosphere.

These rare clouds, sometimes called mother-of-pearl clouds, are 15 - 25km (9 -16 miles) high in the stratosphere and well above tropospheric clouds. They are iridescent but higher and rarer than ordinary iridescent clouds. They occur mostly but not exclusively in polar regions and in winter at high latitudes, Scandinavia, Alaska, Northern Canada.

They shine brightly in high altitude sunlight up to two hours after ground level sunset or before dawn. Their unbelievably bright iridescent colours and slow movement relative to any lower clouds make them an unmistakable and unforgettable sight.